The electroretinogram (ERG) and visual evoked potentials (VEP) are diagnostic tests used to help assess visual system function. See, for example, the textbook Principles and Practice of Clinical Electrophysiology of Vision, 2th edition, edited by Heckenlively and Arden (2006), which describes dozens of diseases that can be diagnosed with the aid of visual electrophysiology. Standards have been developed for the most common of these tests, as described in Marmor et al. (2009), Hood et al. (2012), Holder et al. (2007), and Odom et al. (2010). As a specific example, some features of the clinical ERG are strongly correlated with diabetic retinopathy (Bresnick and Palta (1987), Han and Ohn (2000) and Satoh et al. (1994)). As another example, Kjeka et al. (2013) showed greatly improved outcomes for the treatment of central retinal vein occlusion when basing treatment decisions on ERG results rather than ophthalmologic examinations alone.
Normally, ERG measurements are recorded using a large instrument (e.g., the LKC Technologies UTAS system) in a darkened room with electrodes placed directly onto the eye. Dilating drops are used to enlarge the pupil and anesthetic drops are used to numb the eye before placing the electrodes onto the eye. The eye is stimulated with light to elicit a response from the visual system which is recorded via the electrodes. The measurements are performed by a skilled technician, and the results are usually interpreted by an ophthalmologist or PhD expert in visual electrophysiology. The invasiveness and complexity described above have prevented the ERG from having widespread use in assessing diabetic retinopathy and other diseases.
The invention described in U.S. Pat. No. 7,540,613 helps prevent these disadvantages. Nevertheless, there still exists a need for visual electrophysiology devices that are easier to use and/or have improved performance.